There’s a galaxy protocluster out there in the distant universe that’s waving some tantalizing clues about cosmic history at astronomers. First of all, it’s got an active galactic nucleus—a quasar—at its heart. That’s a black hole emitting huge amounts of radiation. But now, they’ve found at least three young galaxies sending massive amounts of cosmic food (gas and dust) into the maw of that black hole-powered engine. Those infant galaxies are massive and moving fast around each other. And, just to make things interesting, dark matter is probably involved in the action.
All this takes place in what astronomers think is one of the densest regions of galaxy formation in the early universe. The quasar SDSS J165202.64+172852.3 is at the heart of the action and lies 11.5 billion light-years away from us. It’s a very “red” active galactic nucleus. The color is due to some intrinsic characteristic of the galaxy that contains it. But, the quasar is also red-shifted, which makes it look even redder.
So, of course, that made it a perfect target for the James Webb Space Telescope which recently took a look at the quasar. In the process of checking out its emissions, JWST found evidence for the galaxies that are feeding it. The results are already expanding the understanding of how galaxies in the early Universe coalesced into the cosmic web we see today.
A Spectroscopic Look at a Quasar
The team used observations of the quasar made by Webb’s NIRSpec instrument to confirm the existence of the three young massive galaxies. “Our first look at the data quickly revealed clear signs of major interactions between the neighboring galaxies,” shared team member Andrey Vayner of Johns Hopkins University in Baltimore, USA. “The sensitivity of the NIRSpec instrument was immediately apparent, and it was clear to me that we are in a new era of infrared spectroscopy.”
The galaxies feeding the quasar are pretty closely packed together in space. The team believes this marks one of the densest known areas of galaxy formation in the early Universe. “Even a dense knot of dark matter isn’t sufficient to explain it,” said astronomer Dominika Wylezalek of Heidelberg University in Germany, who led the study of the quasar. “We also think we could be seeing a region where two massive halos of dark matter are merging together.”
The whole scene is pretty unprecedented. That’s because astronomers are still working to figure out how and when the first galaxy clusters began to take shape. “There are few galaxy protoclusters known at this early time,” said Wylezalek. “It’s hard to find them, and very few have had time to form since the Big Bang. This may eventually help us understand how galaxies in dense environments evolve. It’s an exciting result.”
Quasars and the Early Universe
In the past few decades, astronomers have found quasars to be handy probes of the early Universe. Their light provides a standard candle to measure distances. When it shines through clouds of gas and dust, quasar light “illuminates” the existence of chemical elements between us and the quasar. However, quasars are now known as beacons that give clues to the existence of infant galaxy clusters that existed less than three billion years after the Big Bang.
That includes protoclusters like the one that contains quasar SDSS J165202.64+172852.3. It’s a chaotic place. It’s a galaxy with a hungry black hole at the core, one of the most powerful known active galactic nuclei. The black hole gets fed by infalling gas from its own galaxy and the three neighboring galaxies. But, it’s also sending out massive amounts of radiation and other emissions to create a strong “galactic wind”. That sends free gas out of its host galaxy. Without gas, star formation comes to an end in the host. The surrounding galaxies get affected, too.
Focusing on the Infant Protocluster
Other telescopes have studied the region around SDSS J165202.64+172852.3, including Hubble Space Telescope and the ground-based Gemini-North. But, untangling the action required the JWST’s NIRSpec instrument. It can actually gather spectra from multiple points of emission, which made it perfect to look at SDSS J165202.64+172852.3 and the galaxies feeding its black hole. Spectral data reveal the motion and speed of galactic winds and outflows to and from the quasar. In particular, NIRSpec was able to see and measure the ionized oxygen in the region. That’s one tracer of the action between the quasar and its neighbors.
The JWST observations are the first of many that astronomers hope to make of this region and of other quasars across different epochs of cosmic history. “To disentangle the incredibly bright light of a distant quasar from the much dimmer host and its companions is almost impossible from the ground. Uncovering the details of the galactic winds that may produce feedback is even more challenging,” commented team member David Rupke of Rhodes College in Memphis, USA. “Now with Webb, we can already see that’s changing.”